Function findBestWaypointInsertionIndices

findBestWaypointInsertionIndices(
    route: Route,
    existingWaypoints: WaypointLike[],
    newWaypoints: WaypointLike[],
): number[]
Multi-waypoint variant of findBestWaypointInsertionIndex.

Projects every existing and new waypoint onto the route exactly once, then returns one insertion slot per new waypoint. The i-th returned index is the slot in existingWaypoints (0 = before origin, existingWaypoints.length = after destination) where the i-th new waypoint falls based on its along-route location.

Multiple new waypoints may share the same slot. Use withInsertedWaypoints when you also need them merged into the existing array in correct along-route order — that helper handles within-slot ranking on top of these slot indices.
Parameters
- route: Route
  The existing calculated route Feature with LineString geometry
- existingWaypoints: WaypointLike[]
  Array of existing waypoints in order (origin, intermediate waypoints, destination)
- newWaypoints: WaypointLike[]
  The waypoints whose insertion slots to compute
Returns number[]
An array of insertion slot indices, one per new waypoint, in input order
Remarks
- Empty newWaypoints returns an empty array.
- Edge cases (empty route geometry, fewer than 2 existing waypoints) return 0 for every new waypoint — i.e. they would all prepend.
- A new waypoint whose projection has no resolvable along-route location also returns 0, matching the singular findBestWaypointInsertionIndex behavior.